The Sun Coral

Aquarists, new or experienced, usually enjoy wandering around marine hobby shops just gawping or watching for that special fish or coral. Perhaps a reef aquarium is being set up and stocking is in progress, or the aquarium has more useable space.

A coral that will catch the eye if it is in stock is the one with the common name of Sun Coral or Orange Cup Coral. The proper name is Tubastraea faulkneri. It comes under the common general title of ‘hard coral’.

The eye is attracted to them because the colour really stands out. The hard coral base is often stone shaped with its upper side covered with a ‘skin’ of orange. The polyps, when extended, are yellow. In the shop the coral size is likely to be 3 to 6″ or so. The aquarist is likely to be drawn to have a closer look. Though it is possible that a new aquarist could successfully maintain the coral, it is better to wait for some experience to accumulate so that the techniques of maintaining consistent high quality within the aquarium have been mastered.

The aquarist with some experience may have an alarm bell ringing in his or her head – very beautiful coral, hmm, there’s bound to be something wrong! Maybe this coral is like the flowerpot coral Goniapora sp or the soft coral Dendronephthya sp. Both are very beautiful and often bought because of it, only for the coral to die as they are particularly difficult to keep. This is a beautiful coral also, maybe it’s the same.

Well, here’s the surprise – it isn’t. Properly cared for in a well maintained aquarium the coral is fairly hardy and has the potential to spread. However, there is one problem (told you so, says the ‘you get problems for super beauty’ experienced aquarist).

Most of the corals that are kept in reef aquaria require good lighting of sufficient intensity and correct spectrum. This is so the zooxanthellae (the single celled algae) within the flesh of the corals can photosynthesize properly, something very important to the health of the coral. However, the Sun Coral doesn’t have any zooxanthellae. The coral is found in the wild in the entrance to caves and other lower lit areas where many other corals cannot go. It may be thought that this is good, as it means the coral can be placed in an area of the aquarium in low light, filling in a gap. This is true up to a point.

The coral needs to get energy from somewhere and this of course means food. As it doesn’t have assistance from zooxanthellae it needs to capture the food. So in the wild it is often in an area of strong currents which will bring food to it, the food being plankton. In the aquarium plankton is in very short supply or missing. Yes, you’ve guessed it; the coral needs to be fed by the aquarist. Failing to feed the coral means it will shrink and die.

Is this a particular problem though? The aquarist’s seawater needs to be of high quality of course and the general aquarium environment the same, but only the aquarist can answer the feeding question. As said, the coral must be fed regularly, it cannot survive on plankton in the aquarium, and general feedings of brine and mysis shrimp will be insufficient as not enough will be captured by the coral. Heavier feeding is likely to cause pollution. The aquarist when purchasing the coral is undertaking the discipline of regular target feeding.

Having got past that point, that is, having accepted the need for ‘personal’ feeding, the aquarist can be fairly confident, though as we all know failure can occur with anything marine for reasons not always clear. However, when the coral arrives home it needs to be acclimated to the seawater, and then placed in an area where there is plenty of seawater movement. The need for light is missing, so the aquarist can place the coral in a spot as required. Generally light is not harmful to the coral, so there isn’t a need for a shady cave etc unless the light is powerful.

Once the coral is in place and has had time to settle over a day or two, the feeding ritual should begin. For this the aquarist will need a supply of frozen brine or mysis shrimp, which will probably already be available anyway because of fish feeding. There is also a need for a syringe with an outlet big enough to allow shrimps to pass through – often a ‘baster’ which is a kitchen utensil with a tube and a rubber bulb at one end will do.

Take some shrimp and defrost it but do not use any heat to assist this – allow it to defrost on its own. Put the defrosted shrimp in a small bowl and using a spoon crush them. Make the result as much like a liquid as possible.

Wait a while after the aquarium lights go off or at least the main ones and only the blue ‘actinics’ are on, draw some of the shrimp liquid into the syringe and very gently, without touching the coral, slowly release the liquid across the polyps of the coral. The polyps may well be closed but this doesn’t matter. Make sure the liquid is released so that the seawater currents assist in moving it across the polyps (if necessary reduce the circulation strength temporarily). There may not be any reaction to the food enticement, but the operation should be repeated each day at the same time. Eventually the polyps will extend in readiness to capture food. As time progresses, they could extend at about the same time each day making life easier for the aquarist. There is little danger of pollution from the shrimp liquid as it will not be in high quantity and other life, maybe other corals, will make use of it.

Once the polyps are extending, the liquid is not fed but the shrimps. They are defrosted as usual but not crushed. Excess liquid is drained off and some seawater added, then the shrimp are drawn into the syringe. In the same way the shrimp are gently expelled into the polyps. Any shrimp that are not captured will float away and will be taken by fish etc. The aquarist may need to keep fish away from the feeding polyps or they may steal the coral’s meal.

Tubastraea sp does not only come in the colour described, but has variations. There is one called the Black Sun Coral, and others could be green or brown. They are all treated the same way.

Provided the aquarist maintains a high quality aquarium environment and successfully feeds the coral, it is possible the coral will create new ‘buds’ and spread. The coral in the aquarium is certainly an eye catcher and worth the effort.